The related art includes drive arrangements for rear-view mirrors of motor vehicles, which allow a mirror head carrying a mirror glass to be moved electrically between a usage position in which the mirror stands substantially at right angles to the vehicle centre axis, and a park position in which the mirror stands substantially parallel to the vehicle centre axis. A majority of drives use an electric motor which, via a two-stage worm gear, rotates the drive housing and a mirror head connected fixedly thereto about an output gear wheel connected to the mirror foot via a torque-limiting safety coupling.
Such an example is known from WO9743144A1 which discloses an electrically actuatable pivot device, a mirror housing (3) of an exterior mirror. The mirror housing can be moved manually from any position to another position, and returned from any position electrically by means of the pivot device to the normal operating position. The mechanism comprises a system of grooves and tabs in engagement therewith for establishing the end positions of the mirror housing.
Attention is increasingly directed at the noise behaviour of the drives. A noise which is different depending on direction may result due to deviations of the rotary axis from the vertical when the mirror head is turned obliquely upward on rotation into the park position, and hence the load on the mirror head is lifted up, and on rotation into the usage position pulls the weight of the mirror head down. To reduce the additional load from the oblique rotary axis, in some cases an axial ball bearing is fitted in the folding drive to reduce friction and hence relieve the load on the electric motor of the drive.
The disadvantage of existing solutions is that the axial ball bearing reduces friction independently of the fold direction of the mirror. So a different running noise is still perceived because of the different counter-moment on the electric motor depending on the direction of rotation. On unfolding, it can also occur that because of gravity, the mirror head advances faster than the gear and a jerky and noisy adjustment results.